| File:S2004s2 040601.jpg Discovery image of Pallene | |
|---|---|
| Discovery | |
| Discovered by | Cassini Imaging Science Team |
| Discovered on | 1 June, 2004 |
| Orbital characteristics [1] | |
| Semimajor axis | 212,280 ± 5 km |
| Eccentricity | 0.0040 |
| Orbital period | 1.153745829 d |
| Inclination (to Saturn's equator) |
0.1810 ± 0.0014° |
| Is a satellite of | Saturn |
| Physical characteristics | |
| Mean diameter | ≈ 4 km |
| Mass | 1.7 − 7 ×1013 kg[2] |
| Mean density | unknown |
| Surface gravity | unknown |
| Rotation period | synchronous |
| Axial tilt | unknown |
| Albedo | unknown |
| Atmosphere | none |
Pallene (pə-lee'-nee, IPA /pəˈliːni/, Greek Παλλήνη) is a very small natural satellite of Saturn lying between the orbits of Mimas and Enceladus.
It was discovered by the Cassini Imaging team led by Carolyn C. Porco in 2004, and given the temporary designation S/2004 S 2. It was actually first seen on August 23, 1981 by Voyager 2 in a single photograph and named S/1981 S 14 and its distance to Saturn was then estimated at 200,000 km. Since it was not visible in other images, its orbit could not be calculated at the time, but recent comparisons have identified it as matching Pallene's orbit [1]. Pallene is also designated as Saturn XXXIII.
Pallene is visibly affected by a perturbing mean longitude resonance with the much larger Enceladus, although this effect is not as large as the Mimas perturbations on Methone. The perturbations cause Pallene's osculating orbital elements to vary with an amplitude of about 4 km in semi-major axis, and 0.02° in longitude (corresponding to about 75 km). Eccentricity also changes on various timescales between 0.002 and 0.006, and inclination between about 0.178° and 0.184° [1].
The names Methone and Pallene have been provisionally approved by the IAU Division III Working Group for Planetary System Nomenclature. They should be officially approved at the IAU General Assembly in 2006. Pallene was one of the Alkyonides, the seven beautiful daughters of the Giant Alkyoneus.
External links
- IAUC 8471 announcing the names (January 21, 2005)
References
- ↑ 1.0 1.1 1.2 J.N. Spitale et al (2006). "The orbits of Saturn's small satellites derived from combined historic and Cassini imaging observations". The Astronomical Journal 132: 692.
- ↑ Based on density 0.5 - 2 g/cm³
- C.C. Porco et al (2005). "Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites". Science 307 (5713): 1226-1236. (February 25, 2005; subscription required)
| edit Saturn's natural satellites |
|---|
| Pan | Daphnis | Atlas | Prometheus | S/2004 S 6 | S/2004 S 4 | S/2004 S 3 | Pandora | Epimetheus and Janus |
| Mimas | Methone | Pallene | Enceladus | Telesto, Tethys, and Calypso | Polydeuces, Dione, and Helene | Rhea |
| Titan | Hyperion | Iapetus | Kiviuq | Ijiraq | Phoebe | Paaliaq | Skathi | Albiorix | S/2004 S 11 | Erriapo | Siarnaq |
| S/2004 S 13 | Tarvos | Mundilfari | S/2004 S 17 | Narvi | S/2004 S 15 | S/2004 S 10 | Suttungr | S/2004 S 12 |
| S/2004 S 18 | S/2004 S 9 | S/2004 S 14 | S/2004 S 7 | Thrymr | S/2004 S 16 | Ymir | S/2004 S 8 |
| See also: Pronunciation key | Rings of Saturn | Cassini-Huygens | Themis |